Biofilms are ubiquitous and can be problematic. Some examples of common biofilms include dental plaque, drain-clogging slime and the slippery coating found on rocks in streams and rivers.
Industrial and commercial problems attributable to biofilms include corrosion of pipes, reduced heat transfer and/or reduced hydraulic pressure in industrial cooling systems, the plugging of water injection jets and the clogging of water filters. In addition, biofilms can cause significant medical problems, for example, by infecting host tissues, by harboring bacteria that contaminate drinking water, and by causing rejection of medical implants.
Biofilms are generally formed when bacteria and/or other microorganisms adhere to surfaces in aqueous environments and begin to excrete a slimy, adhesive substance that can anchor the microorganisms to a wide variety of materials including metals, plastics, soil particles, medical implant materials and animal tissue.
A biofilm is often a complex aggregation of microorganisms comprising a protective and adhesive matrix generated by excretion of polymeric materials, for example, polysaccharides, from the microorganisms. Biofilms are often attached to surfaces, have structural heterogeneity and genetic diversity, and exhibit complex community interactions. Their protective matrix and genetic diversity mean that biofilms are often hard to destroy or otherwise control and conventional methods of killing bacteria, such as antibiotics, and disinfectants, are often ineffective against biofilms.
Because the single cell microorganisms in a biofilm typically are in an attached state, closely packed together and secured to each other and to a solid surface, they are more difficult to destroy than when they are in a free-floating mobile mode, as is the case in many mammalian infections.
A number of proposals have been made for the chemical or pharmaceutical treatment of, or regulation of, the growth of mammalian-resident biofilms. However, as implied above, such methods may be ineffective or subject to resistance or both, or may have other drawbacks commonly associated with pharmaceuticals such as systemic action and side effects.
Some suggestions for treatment of biofilms in humans appear in the patent literature. For example, Bornstein U.S. Patent Application Publication No. 2004/0224288 (referenced “Bornstein” herein) discloses a system and process for thermolytic eradication of bacteria and biofilm in the root canal of a human tooth employing an optical probe and a laser oscillator.
Also, Hazan et al. U.S. Patent Application Publication No. 2005/0261612 discloses a method for decreasing materials such as biofilm attached to a mammalian body which method includes attaching a nanovibrational energy resonator device onto an external or internal area of the body.
Oxley et al. “Effect of ototopical medications on tympanostomy tube biofilms.” Laryngoscope. 2007 October; 117(10):1819-24 describes experiments to examine the effect of ototopical medications on biofilms on fluoroplastic tympanostomy tubes. Reportedly, microbial activity in colony forming units (CFU) was decreased after three weeks. However, despite the treatment, the biofilm was not eradicated but continued to grow. The authors conclude that infectivity of the biofilm can be temporarily neutralized by antibiotic ototopicals and that the biofilm may progress despite treatment.
International patent publication No. WO 00/67917 describes a method for permeabilizing biofilms using stress waves to create transient increases in the permeability of the biofilm. As described, the increased permeability facilitates delivery of compounds, such as antimicrobial or therapeutic agents into and through the biofilm, which agents are apparently to be employed to treat the biofilm.
Desrosiers et al. “Methods for removing bacterial biofilms: in vitro study using clinical chronic rhinosinusitis specimens.” Am J Rhinol. 2007 September-October; 21(5):527-32 describes an in vitro study on removed biofilms from bacterial isolates obtained from patients with refractory chronic rhinosinusitis. As described, the biofilm was treated with both static and pressurized irrigation and a citric acid/zwitterionic surfactant. According to the authors, the pressurized treatment employing irrigant and a surfactant can disrupt the biofilms tested.
Notwithstanding the foregoing proposals, it would be desirable to have new processes and treatments for treatment of biofilms resident in or on mammalian sites.
The foregoing description of background art may include insights, discoveries, understandings or disclosures, or associations together of disclosures, that were not known to the relevant art prior to the present invention but which were provided by the invention. Some such contributions of the invention may have been specifically pointed out herein, whereas other such contributions of the invention will be apparent from their context. Merely because a document may have been cited here, no admission is made that the field of the document, which may be quite different from that of the invention, is analogous to the field or fields of the present invention. Nor is any admission made that the document was published prior to, or otherwise predates, applicant's invention.